Immunophilins are proteins that bind immunosuppressive drugs such as FK506 and rapamycin. Since immunophilin-drug complexes disrupt signaling pathways in cells, understanding their three-dimensional structure and function leads to a better understanding of fundamental biological pathways. Since immunophilin-drug complexes are responsible for the immunosuppression, understanding their structure and function can lead to new, more effective drugs. Immunosuppressive drugs are currently used to prevent the rejection of transplanted organs, but if better drugs could be found, they could be used in autoimmune diseases such as insulin-dependent diabetes, rheumatoid arthritis, and multiple sclerosis. We've been studying the structures of the immunophilins and their complexes with various drugs by X-ray crystallography. The CTC has provided help in analyzing the experimental data, and more importantly, in producing graphics from the results of our studies. For example we were studying two different, but related, immunophilins and needed a way to show both surfaces simultaneously. CTC devised a method to make such images. We're now beginning to study larger complexes and complexes involving two immunophilins linked by specially designed ligands. These larger complexes will outstrip our laboratory computing resources, so we will be doing even more data analysis with the CTC. These multimeric complexes also present serious challenges to graphical representation, and we will undoubtedly continue to use the facilities at the CTC for this purpose as well